Anti-resistance method

ABSTRACT

The decrease in soybean rust control using fungicide mixtures (DMAs+QoIs) reached very low levels for the harvest of 2012/13 (an average of 37% for the three main mixtures). This decrease is due to a decrease in Pp sensitivity to individual DMIs and QoIs, and mixtures thereof. Anti-resistance strategies have not been introduced in Brazil for preventing/delaying the development of resistance of the fungus that is the casual agent of rust ( Phakopsora pachyrhizi ) in soybean [plant form the family Fabaceae,  Glycine max  (L.) Merr.] and of the fungus that is the casual agent of yellow leaf spot ( Drechslera tritici - repentis ) in wheat [plant of the family Triticea,  Triticum aestivum  L.], as well as other disease complexes that attack the main crop plants in Brazil, such as corn, beans, cotton, inter alia. By means of said method it is possible to recover the efficiency of several mixtures (DMI+QoI and QoI+SDHI) due to a decrease in fungal sensitivity. The methods described by the present invention seek to increase the effective useful life of fungicides and increase grain yield.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for preventing/delaying thedevelopment of resistance of the fungus that is the causal agent of rust(Phakopsora pachyrhizi) in soybean [plant from the Family FabaceaeGlycine max (L.) Merr.] and of the fungus that is the causal agent ofyellow leaf spot (Drechsiera tritici-repentis) in wheat [plant of theFamily triticeous Triticum aestivum L.]. By means of said method it ispossible to recover the efficiency of some mixtures (DMI+QoI andQoI+SDHI) due to a decrease in fungal sensitivity. The methods describedby the present invention aim at increasing the effective life offungicides and increase grain yield. Furthermore, said method can alsobe used for resistance of the causing fungi of other diseases thatattack crops plants, such as corn and cotton.

BACKGROUND OF THE INVENTION

In Soybean Cultures.

Two rusts are reported in soybean cultures. The first called American iscaused by Phakopsora meibomiae Arthur and the second called Asian rust(ASR) caused by Phakopsora pachyrhizi Sydow.

The fungus that causes soybean rust belongs to the class ofbasidiomycetes. The species is called Phakopsora pachyrhizi Sydow.

In the specific case of Brazil, the rust was detected in the years2001/02 and in the very next crop began their control with fungicides.At this time, fungicides “triazoles” alone were applied over a largearea with many applications in the soybean production cycle. In the2005/06 crop some producers (notably in the Brazilian Midwest)complained for the first time, of the rust control failure with the useof these fungicides (mainly DMI). Research conducted in experimentalfield and laboratory confirmed the reduced sensitivity (resistance) offungal strains to triazole fungicides.

In the 2013/14 crop were cultivated 29.4 million hectares, with a yieldof 3.0 t/ha, with a total production of 82.6 million tons of soybeans.

According to a survey conducted by Kleffmann (2014), in this lastsoybean crop, on average, three applications/ha were made for thecontrol of P. pachyrhizi (Pp). However, in regions where the second cropof soybeans is cultivated up to 11 applications/ha were made in the samearea. This practice speeds up the selection of Pp mutants withresistance to fungicides.

The extension of the treated area, the isolated use of fungicides sitespecific and the large number of applications in the same crop, facedwith anti-resistance strategies recommended by the FRAC (2012) toprevent or delay the emergence of resistant strains, show earlyoccurrence of the risk of Pp resistance to fungicides in Brazil.

It is known from the prior art that fungicides used in soybean and wheatcrops fall into two chemical groups with site specific mechanism ofaction, which are: triazoles, or demethylation inhibitors(DMIs)—included therein the tebuconazole, which for a long time was veryefficient; and strobilurins, or outside quinone inhibitors (QoIs). Morerecently a third chemical group has been used, namely the enzymesuccinate dehydrogenase inhibitors (SDHI). The combination of the DMIswith QoIs has been used for more than 12 crops for the control of ASR.Additionally, reducing the sensitivity of Pp to DMI burdened fungicidalaction of QoIs in the mixtures. From the 2012/13 crop it was noted thatPp sensitivity was reduced to mixtures of DMIs+QoIs and QoIs+SDHI). Morethan 50% of soybean areas in Brazil receive a second annual crop, whichis called “safrinha” (when it is corn/cotton) or “winter crop” (in thesouthern regions, with winter crops for wheat, oats, canola, rye etc.).This fact causes various populations of fungi to e also be selected, andcauses them to become increasingly resistant to fungicides and mixturesabove referenced.

In Wheat.

The fungus that causes the yellow leaf spot of wheat belongs to theclass of Imperfect Fungi and is called Drechsiera tritici-repentis(Died) Shoemaker (Dtr) in anamorphic form and Pyrenophoratritici-repentis (Died.) Drechsler in teleomorphic. The yellow leaf spotof wheat was recorded in Australia (Rees & Platz, 1979), Canada (Wright& Sutton, 1990) and the United States (Hosford, 1981). In South America,Dubin (1983) found it in Colombia, Ecuador and Peru. In Argentina it wasfirst observed to the north of Buenos Aires Province in the 1980s(Annone, 1985). In Brazil, the first reference about this disease wasmade by Costa Neto (1967), having the same being detected in Rio Grandedo Sul, in 1959, in the city of Dom Pedrito. Later, Mehta (1975)reported the occurrence of an epidemic of the disease in the state ofParana.

In Brazil, until 1976, it was not allowed the use of fungicides in wheataerial organs. A milestone for its use was the UNDP/FAO Agreement withthe Experimental Station of Passo Fundo, of the Ministry ofAgriculture—today Embrapa Wheat.

In wheat crops, on average, three applications per ha/crop are usuallymade.

According to prior art information, the first attempts to applyfungicides in the aerial part of the wheat crop was around the year 1958by researchers from the Federal University of Pelotas (today EmbrapaClima Temperado), to control the disease giberela.

At the time, the South-Brazilian Commission of Wheat Researchrecommended applications of fungicide at booting and flowering, whichwas used for a decade (between 1976 and 1986), until the recommendationof triadimefom.

In the wheat crop of 2003 technical assistants and producers complainedfor the first time, about the failure to control leaf spots aftercontinuous use for 20 years of DMI+QoI fungicides.

The area cultivated with wheat crop in 2012/14 reached 2.2 million ha.Control of the disease known as “tan spot of wheat” was made with theuse of mixtures, but with very poor (<50%) and inefficient response, dueto the development of resistance. Therefore, companies and researchinstitutions are committed to developing an anti-resistance strategy, sothat the said disease control efficiency is back to the 80% to 90%level.

Sensitivity Reduction (SR) of Fungi to Fungicides.

It is known that sooner or later, during the years of commercial use ofa fungicide, may arise a mutant individual in the target pathogenpopulation that is not sensitive enough to be controlled satisfactorily.It multiplies increasing its population silently.

Generally, the SR is in response to the repeated use of a fungicide withthe same mechanism of action, in a large area with many applications inthe crop cycle. The first evidence of this change is observed by theproducer, that complains about “control failure.” In this situation thecontrol went from “efficient and economic” to “inefficient anduneconomical.”

With respect to the term “sensitivity reduction”, the term “reduction”should be used, preferentially, instead of the term “loss ofsensitivity.” SR is proven in the lab when there is an increase insensitivity reduction factor, i.e., SRF (>1).

The term is used to previously sensitive fungal strains, which, throughvariation mechanism such as mutation, significantly reduced theirsensitivity to fungicide (SRF>1.0).

The science of fungicides describes the resistance of a fungus to afungicide with site specific mechanism of action (for example, DMI, QoIand SDHI) can be cross or multiple. Cross-resistance occurs within thesame group, as for triazoles (cyproconazole, epoxiconazole andtebuconazole), and also for strobilurins (azoxystrobin, picoxistrobia,pyraclostrobin and trifloxystrobin). However, it is worth noting theoccurrence of multiple resistance when the same strain of the fungus hasa reduced sensitivity both with respect to triazoles as with respect tostrobilurins.

With regard to soybean, particularly with soybean rust, it is likelythat both the cross-resistance and the multiple are occurring; i.e.,resistance to all triazoles and all strobilurins. And in wheat, it wasproved that only cross-resistance is being checked.

The situation proved, on this account, to be worrying. Faced with thisfact, companies and institutions began to wonder what could be done torescue the control levels (between 80% and 90%) of triazoles andstrobilurins, isolated or in mixture.

Reduction of Chemical Control Efficiency

a. Soybean Rust—Demethylation Inhibitors (DMIs)-Fungicides

As occurred with flutriafol, tebuconazole has become widely used andwith high efficiency, being the reference fungicide in controlling rust,but not for long.

In order to clarify the facts, experiments conducted at the FoundationMT, Rondonopolis, by the University of Rio Verde and institutionsparticipating in the Cooperative Tests of Fungicides (beginning in the2003/04 crop), confirmed the reduction of control efficiency. It wasproved the reduction of control effectiveness by comparing theperformance of DMIs in the 2005/06 crop with the (2012/13) crop inresults of research conducted at the University of Rio Verde. In the2005/06 crop, the average rust control by DMIs was 90.3. After eightyears, corresponding to the 2012/13 crop, the control of DMIs was 52.0with a reduction in efficacy of 42% (Table 1). (problem)

TABLE 1 Reduced soybean rust control by DMIs fungicides appliedpreventively in control (%) and control reduction Crops ReductionFungicide 2005/06 2012/13 (%) Cyproconazole 96.0 52.0 45.9 Epoxiconazole80.0 40.0 50.0 Tebuconazole 95.0 64.0 32.8 Average 90.3 52.0 42.0Source: Silva et al., 2013.

The reduction of the sensitivity of Pp to tebuconazole and cyproconazolefungicides, controlling only 42 and 38%, respectively, was alsodemonstrated by Godoy and Palaver (2011). At this time, the mixturestill showed no reduction in efficiency; cyproconazole+azoxystrobin, 72%and epoxiconazole+pyraclostrobin, 88% control with an average of themixtures of 80% of control. Probably, at this time, the efficiency wasensured by QoIs as the average of the DMIs was only 40% (Table 2).

TABLE 2 Control reduction of soybean rust severity, evaluated by thearea under the disease progress curve (AUDPC) by some fungicides in crop2010/11 Severity Control Treatments (%) (%) Control 74.0 a —Tebuconazole 49.9 b 42 Cyproconazole 58.1 b 38 Cyproconazole + oazoxystrobin 14.8 c 72 Epoxiconazole + pyraclostrobin 9.0  88 Source:Modified Data of Godoy and Palaver (2011).

An example that reinforces the reported fact is the gradual reduction oftebuconazole control over the crops using it covering the periodbeginning in 2004/05 to 2013/14 (as FIG. 1).

From the 2003/04 crop, soybean rust control efficiency (ASR) bytebuconazole, was reduced by 7.2% per year (see also FIG. 1).

Therefore, the fact is that today there is a problem that lies in thefact that with this reduction in speed in two more crops, it is likelythat soybean rust control by tebuconazole reaches zero. So againcompanies are faced with the problem of how producers can takeprecautions to ensure ASR control over 80%? And yet, what would be theamount of damage from lack of anti-resistance strategy? (problems)

Soybean Rust—Qols Fungicides

The reduction of control by the mixtures can also be attributed tosensitivity reduction of Pp to QoIs. From the 2008/09 crop was detectedearly reduction in the control of azoxystrobin and reached only 16% ofcontrol in the 2013/14 crop (see FIG. 6).

Using the equation y=−13.8x+92.8, it was determined that from 2009/10the efficacy of this fungicide has been reduced by 13.8% per year andending by reaching in the 2013/14 crop, only 16% of control (see FIG.6).

Comparing the reduction of tebuconazole control with the azoxystrobin,the current level of control is similarly low. However, the differenceis in the shortest time required by DMI and higher with QoI to achievethis same level “low”

Soybean Rust—Fungicide Mixtures Composed of DMI+QoI

What has been checked with the latest crops is the reduction of rustcontrol by mixtures of triazoles+strobilurins. Questioned whether thelow control presented by mixtures can be attributed to greater reductionof the sensitivity of the fungus to DMIs. Or, if the lower control ofthe mixtures can be attributed to reduced sensitivity of Pp to QoIs.

The results of cooperative tests of fungicides, coordinated by EmbrapaSoybean, Londrina, can bring the answer to these questions. Thefollowing graphs of FIGS. 2, 3, 4 and 5 show the reduction of rustcontrol by fungicide mixtures traditionally used in soybeans over thepast crops.

An example with cyproconazole+azoxystrobin mixture is shown in FIG. 2.This mixture has been used since 2003/04, when it exhibited anefficiency of 90%.

Using the equation y=−6.5429x+90.067, you can calculate that from the2007/08 crop the effectiveness of this mixture has been reduced by 6.54%per year, reaching in the 2013/14 crop only 41% of control (see FIG. 2).

Using the equation y=−9.0x+100.0, one can calculate that from 2008/09the effectiveness of the mixture cyproconazole+azoxystrobin has beenreduced by 9.0% per year, reaching 37% control in the 2013/14 crop (seeFIG. 3).

The mixture “epoxiconazole+pyraclostrobin” has been used since 2007/08.With the equation y=−12.6x+99.0 [where y=control (%) and x=thepercentage of annual reduction of control], you can calculate that fromthe 2009/10 crop the effectiveness of this mixture has been decreased by12.6% per year, reaching in the last crop 23% (see FIG. 4).

According to the equation y=−9.0x+100.0, from the 2008/09 crop theaverage effectiveness of mixtures “cyproconazole+azoxystrobin”,“cyproconazole+picoxystrobin” and “epoxiconazole+pyraclostrobin” oversix crops has been reduced by 9.0% per year, reaching 37% in the lastcrop (see FIG. 5).

In Wheat

In the 2003 wheat crop for the first time, there was complaint of leafspot control failure after continuous use of fungicides DMI+QoI, for 20years. Until that time there were few reports of the sensitivity of thefungus that is causal agent of yellow spot to fungicides (Stolte, 2006;Tonin, 2009; Beard et al, 2009; Patel et al, 2012). The referenceconcentrations of sensitivity of Dtr to fungicides found in theliterature were 0.17 mg/L in average for the epoxiconazole,propiconazole and tebuconazole. Hunger & Brown, determined an IC50 of0.04 mg/L for propiconazole and 0.19 for tebuconazole; Beard et al,determined IC50 of 0.19 mg/L for epoxiconazole and 0.25 mg/L fortebuconazole). Comparing these values with the sensitivity of isolatesof Brazil proves the reduced sensitivity occurring here (see Table 3).

TABLE 3 Concentrations for 50% inhibition of mycelium growth (IC₅₀) offive isolated from Drechsiera siccans for five fungicides DMIs Isolated(IC50 mg/L) Fungicide 01/F30 02/RZ 03/SF 04/F52 05/VQ AverageCyproconazole 0.36 0.47 0.32 0.44 0.29 0.37 b Epoxiconazole 0.28 0.280.40 0.32 0.40 0.33 b Propiconazole 0.32 0.51 0.30 0.30 0.30 0.34 bProthioconazole 0.22 <0.1 0.26 0.25 0.14 0.21 c Tebuconazole 0.66 0.490.65 0.61 0.44 0.57 a Average 0.36 0.37 0.38 0.38 0.31 CV (%) 9.05

Averages followed by the same letter do not differ by 5% of the Tukeytest. Average of two experiments.

However, the highest reduction of sensitivity of the Dtr to fungicidesand what better explains the control failure claimed by producers is theCI50 obtained for QoIs fungicides (see Table 4).

TABLE 4 Inhibitory Concentration of 50% of the spore germination (CI50)of fungicides for five isolates of Drechsiera tritici-repentis tostrobilurin fungicides Isolated (CI₅₀ mg/L) Fungicide 01/QTZ 02/ONX03/HZT 04/GUA 05/CD Average Azoxystrobin A > 40 a A > 40 a A > 40 a A >40 a A > 40 a A > 40 a Kresoxim methyl A > 40 a A > 40 a A > 40 a A > 40a A > 40 a >40 a Picoxystrobin A > 40 a A > 40 a A > 40 a A > 40 a A >40 a >40 a Pyraclostrobin D 0.75 b B 0.85 b C 0.78 b E 0.58 b A 1.03 b0.80 b  Trifloxystrobin A > 40 a A > 40 a A > 40 a A > 40 a A > 40 a >40a Average  C > 32.15  B > 32.17  C > 32.15  D > 32.11  A > 32.20 CV (%)0.02

Averages followed by the same letter do not differ there between by 5%of the Tukey test. Lowercase compare average in the column and capitalletters in the line. Average of two experiments.

Taking as Cl₅₀ standard of sensitivity, 0.75 mg/L (Table 4) obtained forpyraclostrobin, it is calculated the reduction factor of the sensitivityof the Dtr to QoIs fungicides (see Table 5).

TABLE 5 Reduction factor of the sensitivity of Drechslera tritici-repentis to QoIs fungicides. Isolated Fungicide 01/QTZ 02/ONX 03/HZT04/GUA 05/CD Average Azoxystrobin A > 53 a A > 53 a A > 53 a A > 53 aA > 53 a >53 a Kresoxim methyl A > 53 a A > 53 a A > 53 a A > 53 a A >53 a >53 a Picoxystrobin A > 53 a A > 53 a A > 53 a A > 53 a A > 53a >53 a Pyraclostrobin D 1.0 b B 1.13 b C 1.04 b E 0.77 b A 1.37 b 0.1.1b  Trifloxystrobin A > 53 a A > 53 a A > 53 a A > 53 a A > 53 a >53 a CV(%) 0.02

Cl50 of sensitivity reference of 0.75 mg/L.

When the SRF is close to 1.0 there is no reduction of sensitivity.However, if >1 with different magnitude, it indicates reducedsensitivity of fungi to fungicides. In this case SRF ranged from 1.04to >53 (see Table 5).

Regarding the state of the art related to patent documents, literatureis very broad and comprehensive, although no document reported on thesolution to the technical problem, as will be described herein. Just asan example, it stands out:

The aforementioned examples related to soybean and wheat have been sofar the most studied due to pathogens Pp and Dt provide amplitude ofdamage above 50% in their respective crops. However, the concept ofresistance should also be extended to all crops including cotton, corn,beans, among others.

Regarding the state of the art related to patent documents, literatureis very broad and comprehensive, although no document reported on thesolution to the technical problem, as will be described herein. Just asan example, it stands out: International patent application WO2012040804 A2, entitled: “Synergistic combinations of triazoles,strobilurins and benzimidazoles, uses, formulations, productionprocesses and applications using the same”, which describes anagrochemically synergistic formulation of triazoles, strobilurin andbenzimidazoles, in specific proportions to control and/or combat pestsand diseases in crops. Also described are their preparation process, useand method of use, as well as the use of triazoles, strobilurin andbenzimidazoles in the preparation of a synergistic agrochemicallyformulation of the invention.

European patent application EP 2719280 A1, titled “Use ofN-phenylethylpyrazole carboxamide derivatives or salts thereof forresistance management of phytopathogenic fungi,” which refers to the useof derivatives of carboxamide pyrazole-ethyl-N-phenyl, in particular3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid[2-(2,4-dichlorophenyl)-2-methoxy-1-methylethyl] amide for resistancemanagement of phytopathogenic fungi on crops and describes a method forresistance management of phytopathogenic fungi in various crops.

In view of all the foregoing, in order to recover the control levels ofsome fungicides, the present invention developed a method forpreventing/delaying the development of fungal resistance in some cropssuch as soybeans, wheat, cotton, corn and beans, more specifically tothe fungus that is causal agent of soybean rust and the fungus that iscausal agent to yellow leaf spot of wheat.

SUMMARY OF THE INVENTION

The present invention introduces in the Brazilian system of productionof soybean, wheat, cotton, corn, beans among others, an anti-resistancehighly effective strategy, pioneer of these crops in Brazil. It consistsof adding a fungicide “manganese ethylene bis(dithiocarbamate)+Zn” multisite, to any mixtures of fungicides, DMIs, QoIs and SDHI in allcombinations and applications.

OBJECTS OF THE INVENTION

Considering the reduction in the control of DMIs, isolates QoIs, andmixtures, the present invention aims to increase the useful life of thefungicidal mixtures “DMIs+QoIs” or “QoIs+SDHIs”, now with reducedcontrol due to reduced sensitivity of Pp and Dtr to the mixtures.

Another object of the present invention aims to preserve and/or delaythe reduction of the sensitivity of Pp and Dtr mixtures containing“carboxamides+QoI,” “prothioconazole+QoI,”“prothioconazole+QoI+carboxamide” and “QoI+carboxamides”. Moreprecisely, increased fungitoxicity is achieved by adding a multi-sitefungicide to the mixtures.

DESCRIPTION OF THE FIGURES

FIG. 1. Reduced soybean rust control by tebuconazole over eleven crops.(Source: Cooperative tests of fungicides).

FIG. 2. Control Reduction of soybean rust by cyproconazole+azoxystrobinmixture over six crops. (Source: Cooperative tests of fungicides).

FIG. 3. Control Reduction of soybean rust by cyproconazole+picoxystrobinmixture over six crops. (Source: Cooperative tests of fungicides).

FIG. 4. Reduction control of soybean rust byepoxiconazole+pyraclostrobin mixture over six crops. (Source:Cooperative tests of fungicides).

FIG. 5. Average reduction of soybean rust control by mixtures ofcyproconazole+azoxystrobin, cyproconazole+picoxystrobin andepoxiconazole+pyraclostrobin over six crops. (Source: Cooperative testsof fungicides).

FIG. 6. Control Reduction of soybean rust for azoxystrobin over sixcrops. (Source: Cooperative tests of fungicides).

DETAILED DESCRIPTION OF THE INVENTION

In order to solve some of the problems found in the prior art—that is,to rescue the control levels (between 80% and 90%) of triazoles,strobilurins, carboxamides, isolated or in mixture—the present inventiondeveloped a method for preventing/delaying the development of fungalresistance in some crops such as soybeans, wheat, cotton, corn andbeans, specifically for the fungus that is the causal agent of rust(Phakopsora pachyrhizi) of soybean (plant of the Family Fabaceae Glycinemax (L.) Merr.), and the fungus that is the causal agent of yellow leafspot—(Drechsiera tritici-repentis) of wheat (plant of the Familytriticeous Triticum aestivum L.) and all other disease complexesincluding these two crops and all other disease complexes of grain cropsin Brazil such as corn, cotton, beans and other of minor importance.

By the said method it is possible to recover the efficiency of somemixtures (MDI+QoI) due to increased fungitoxicity of mixtures.

The fungus resistance retarding technique consists of:

add to the spray tank, mancozeb (manganese ethylenebis(dithiocarbamate)+Zn), multi-site fungicide, mixtures ofdemethylation inhibitor fungicides (DMIs), quinone outside inhibitors(QoI) and succinate dehydrogenase inhibitors (SDHI) currently in use.The amount of mancozeb can vary between 1.0 kg/ha and 5.0 kg/ha,preferentially between 1.0 kg/ha and 4.0 kg/ha, most preferentiallybetween 1.0 and 3.0 kg/ha, together with the fungicide (mixture ofprefab “DMI+QoI” or “QoI+SDHI”) in all of their combinations andapplications;

trigger the spray tank agitator; and

once the syrup is homogenized, apply the syrup in crops.

The anti-resistance strategy of the present invention is the addition ofthe multi-site protective fungicide, e.g. mancozeb, mixtures of“DMIs+QoIs” or “QoIs+SDHIs” in control of soybean rust and yellow spotof wheat leaf and other diseases complexes in all crops. The addictionof the multi site protective is given with a first mobile penetratingfungicide (QoI) and subsequently with a second mobile penetratingfungicide (DMI or SDHI).

In the case of soybean rust, the facts showed that the resulting controlof the mixtures use of 80% of two fungicides specific site(strobilurins+triazoles) was not durable. So much that, after five cropsof continuous use, producers reported the failure of said control.

Experiments conducted at various locations in Brazil showed theefficiency of mancozeb (manganese ethylene bis(dithiocarbamate)) appliedalone to control soybean rust and yellow spot of wheat leaf. However,its greatest contribution was proven when added to commercial blendsbringing control to values of up to 80%, similar efficiency of mixtures“triazole+strobilurin” at the beginning of its use.

The results showed that the addition of mancozeb improved theperformance of all the mixtures tested. Therefore, the present inventionused the same strategy as the solution to recover the original controllevels (>80%) and make the useful life of the fungicides longer incontrolling the target disease of the invention. This is because,mancozeb, being a multi-site protective fungicide and presenting a broadspectrum of action, will also contribute to the control of otherdiseases in soybean and also in wheat.

It is important to note that the method of the present invention,although quite simple, should be understood as innovative and veryimportant for the sustainability of soybean and wheat cultures in Braziland worldwide. First, because until then, the control of soybean rustand yellow spot in wheat showed to be inefficient. Second, because withmixtures “triazole+strobilurin” it was the latter that made the controland technical scholars understood that it would not be feasible thedevelopment of resistance to strobilurins, which unfortunately ended uphappening. This is because the fungus used a new biochemical mechanism,hitherto unknown, to face the fungicide (QoIs) and not be eliminatedfrom the environment.

The method of the present invention aims at increasing the effectivelife of fungicides and increase grain yield.

It was clearly demonstrated, on the background of the invention, the useof the multi-site protective fungicide “manganese ethylenebis(dithiocarbamate)+Zn” as the mechanism of action for recovering thecontrol efficiency of the mixtures that showed reduced efficacy due toreduced sensitivity of the fungus to these active ingredients.

Thus, in order to solve the prior art drawbacks related primarily tosoybean and wheat, the present invention aims to provide a method fortreating soybean rust and wheat yellow spot with the addition ofmulti-site fungicides to the existing commercial mixtures.

The multi-site fungicides, such as mancozeb, act at least in sixbiochemical mechanisms of the fungus cell, hampered or preventingdevelopment of resistance. This is the most reliable tool in the fightagainst the development of resistance of fungi to fungicides.

EXAMPLES

In Soybean.

A study was conducted to determine the contribution of the mancozebaddition to mixtures of “strobilurin+triazoles.” The experiments wereconducted in the field, in nine different locations, where it wasdetermined the fungi toxicity of mancozeb to soybean rust.

Two doses were tested (1.5 and 2.0 kg/ha) with various numbers ofmancozeb applications. The effect of mancozeb (1.5 kg/ha), incorporatedinto commercial mixtures was also tested.

The experiments were conducted with soybean cultivar Monsoy 9144 RR.Mancozeb formulation 750 WDG (water dispersible granules) was used,commercially available, for application of mancozeb according to Tables6 and 7.

TABLE 6 Control (%) of soybean rust by mixing “DMI + QoI” added or notmancozeb, applied three times in two groups of phenological stages ofsoybean, evaluated by the area under the disease progress curve (AUDPC).Rio Verde - GO Mancozeb Mixtures Without With RI Cyproconazole +Azoxystrobin 42.8 74.0 31.2 Cyproconazole + Pycoxistrobin 74.0 79.4 5.4Tebuconazole + Pycoxistrobin 74.0 85.9 11.9 Average A 66.1  B 79.8  13.7Severity in the control = 70%. CV = 4.60%. RI = Relative Increase ofControl.

TABLE 7 Control (%) of soybean rust by mixtures “DMI + QoI” added or notmancozeb, applied three times at different growth stages and assessed bythe severity in leaflet - Passo Fundo - RS Mancozeb Mixtures WithoutWith RI Cyproconazole + Azoxystrobin 68.6 89.8 21.2 Epoxiconazole +pyraclostrobin 40.5 75.2 34.7 Tebuconazole + Pycoxistrobin 64.4 79.014.6 Average A 57.8  B 81.3  23.5 Severity in the control = 37.3%. CV =6.45%. RI = Relative Increase of Control.

From the experimental results, we found that the addition of thefungicide protective target not only reduces the risk of resistance, butprimarily reverts control to the original level of 80%, and achieveresults also in the yield increase of soybean grain.

In wheat. Due to reduced sensitivity of Dtr, mainly to QoIs, control ofleaf spot has been very low (15.5% as shown in Table 8).

With the addition of mancozeb, by using the method anti-resistancedescribed in the present invention, the control has been quite improved(33.3% also as shown in Table 8).

TABLE 8 Control (%) of the wheat leaf spots mixtures of DMI + QoI withor without mancozeb added. Evaluation 14 days after the firstapplication Mancozeb Fungicide Without With Cyproconazole + Azoxystrobin0 30 Cipro. + azoxy + propiconazole 23 38 Epoxiconazole + pyraclostrobin19 36 Tebuconazole + methyl crezoxim 15 39 Tebuconazole +trifloxystrobin 17 29 Prothioconazole + trifloxystrobin 17 28 Average15.2 33.3

Thus, in view of the above reported tests, it was found that theaddition of mancozeb increased control of rust and wheat yellow spotwith the conventional fungicide “DMI+QoI”. This can also be extrapolatedto other disease complexes in other crops as above mentioned.

In view of the foregoing it can be said that one advantage of the methoddescribed herein is to use the multi site fungicide mancozeb, sincehitherto, there are known cases of fungi resistant to it. Therefore, itappears as an essential tool in the fight against soybean rustresistance to fungicides DMIs, QoIs, and mixtures thereof. It wasfurther found that the lower the performance of the mixture in rustcontrol, the greater the added benefit of mancozeb. Furthermore, theaddition of the dithiocarbamate (such as mancozeb) resulted in betterdisease control and plant productivity. Therefore, said method isregarded as innovative and very important for the soybean cropsustainability in Brazil and worldwide.

It was concluded therefore that the addition of a fungicide multi siteprotective, such as mancozeb, for the combined products (registered forcontrol of Asian soybean rust and wheat yellow spot) regains control andprimarily prevents the future development of fungal resistance.

It is important to emphasize that although the present invention hasexemplified its application in soybean and wheat cultures, the patentholder states that the method described herein may also be applied toother cultures, such as, for example, corn, cotton and bean.

The present invention is more specifically explained by the examplesabove. However, it should be understood that the scope of the presentinvention is not limited to the examples in any respect. It can be seenby one skilled in the art that although the present invention includesthe previously reported examples, modifications and changes can be madewithin the technical scope of the present invention.

The invention claimed is:
 1. An anti-resistance method for preventing ordelaying the development of a fungal disease in a soybean or wheat crop,the method comprising: (i) adding to a spray tank, mancozeb (manganeseethylene bis(dithiocarbamate)+Zn) in an amount of 1.0 kg/ha to 5.0kg/ha, and a prefabricated mixture of fungicides comprising: a quinoneoutside inhibitor fungicide (QoI), which is a strobilurin, and ademethylation inhibitor fungicide (DMI), which is a triazole; (ii)triggering spray tank agitator to form a homogenized syrup; and (iii)applying the homogenized syrup to the crop; wherein Phakopsorapachyrhizi is a causal agent of rust in the soybean crop, and Drechsleratritici-repentis is a causal agent of yellow leaf spot in the wheatcrop, and wherein the addition of the mancozeb to the quinone outsideinhibitor and the demethylation inhibitor increases the resistance ofthe crop to the disease in comparison to the method lacking mancozeb. 2.The method according to claim 1, wherein applying the homogenized syruprescues control levels of the disease between 80% and 90%.
 3. The methodaccording to claim 1, wherein the application of the homogenized syruppreserves or retards sensitivity reduction of P. pachyrhizi andDrechsiera tritici-repentis of the mixture comprising prothioconazole asthe demethylation inhibitor.
 4. The method according to claim 1, whereinthe mancozeb is added in the amount between 1.0 and 4.0 kg/ha.
 5. Themethod according to claim 1, wherein the mancozeb is added in the amountbetween 1.0 kg/ha and 3.0 kg/ha.